C++ Program

A more advanced use of macros is also permitted by the preprocessor. This involves macros which accept parameters and hand back values. This works by defining a macro with some dummy parameter, say x. For example: a macro which is usually defined in one of the standard libraries is abs() which means the absolute or unsigned value of a number. It is defined below: #define ABS(x) ((x) < 0) ? -(x) : (x) The result of this is to give the positive (or unsigned) part of any number or variable. This would be no problem for a function which could accept parameters, and it is, in fact, no problem for macros. Macros can also be made to take parameters. Consider the ABS() example. If a programmer were to write ABS(4) then the preprocessor would substitute 4 for x. If a program read ABS(i) then the preprocessor would substitute i for x and so on. (There is no reason why macros can’t take more than one parameter too. The programmer just includes two dummy parameters with differe...